[Progress in possible effects of BCG vaccine on the prevention of SARS-CoV-2 infection: An update]

Area of Science:

• Immunology
• Infectious Diseases
• Vaccinology

Background:

• Global efforts to develop a COVID-19 vaccine face challenges including viral mutation and antibody-dependent enhancement (ADE).
• The absence of specific treatments necessitates exploring alternative protective measures against SARS-CoV-2.
• Epidemiological observations suggest a potential correlation between Bacillus Calmette-Guerin (BCG) vaccination policies and reduced COVID-19 incidence and mortality.

Purpose of the Study:

• To investigate the potential protective effects of the BCG vaccine against SARS-CoV-2 infection.
• To explore the hypothesis that BCG vaccination may confer cross-protection against COVID-19 via trained immunity.
• To provide evidence for the use of BCG as an alternative public health intervention during the COVID-19 pandemic.

Main Methods:

• Review of epidemiological data comparing COVID-19 outcomes in countries with and without BCG vaccination policies.
• Analysis of the proposed "trained immunity" mechanism of BCG.
• Initiation and ongoing conduct of clinical trials to assess BCG's efficacy against SARS-CoV-2.

Main Results:

• Countries with long-term BCG vaccination policies generally exhibit lower rates of COVID-19 cases and mortality.
• Preliminary data suggests a potential association between BCG vaccination and reduced severity of SARS-CoV-2 infection.
• The "trained immunity" effect is a plausible mechanism for BCG-mediated protection.

Conclusions:

• BCG vaccination may serve as a potential, readily available intervention to mitigate the impact of the COVID-19 pandemic.
• Further clinical research is crucial to confirm the preventive and therapeutic benefits of BCG against SARS-CoV-2.
• BCG's established safety profile makes it an attractive candidate for exploring repurposed vaccination strategies.